Yeah don't use the brush to adjust the background, a tip I learned off LisaJH is to use the quick selector tool and then refine the edge. It'll do a much better job around the hair and you won't end up with the "pasted on" look.
For what it's worth, she has lovely cheek bones but you're lighting her face very flat, especially in #1 and #3. This is very unflattering for her face shape and makes it look rounder than it actually is. Experiment with the lighting angles to try and show the natural contours of her face.